Wireless Local Bridges
Wireless Local Bridges
Network bridges are an important part of any network: They connect multiple LANs at the
MAC layer to produce a single logical network. The MAC layer, which provides medium
access functions, is part of IEEE’s architecture describing LANs. The functionality of the
MAC Layer, along with the Logical Link Control (LLC), fits within the Data Link layer of
ISO’s OSI Reference Model. Chapter 3, “Overview of the IEEE 802.11 Standard,” describes
how the LLC works. Bridges interface LANs together, such as ethernet to ethernet or ethernet
to token ring, and also provide a filtering of packets based on their MAC layer address. This
enables an organization to create segments within an enterprise network.
If a networked station sends a packet to another station located on the same segment, the
bridge will not forward the packet to other segments or the enterprise backbone. If the packet’s
destination is on a different segment, however, the bridge will allow the packet to pass through
to the destination segment. Thus, bridges ensure that packets do not wander into parts of the
network where they are not needed. This process, known as segmentation, makes better use of
network bandwidth and increases overall performance.
There are two types of bridges:
• Local bridges These connect LANs within close proximity.
• Remote bridges These connect sites that are separated by distances greater than the
LAN protocols can support. Most companies that develop wireless LAN NICs also sell a wireless local bridge referred to
as an access point that makes available connections to wired network-based servers and
enables multiple wireless cell configurations. The filtering process of a local bridge (whether it
is a wireless or wired type) is critical in maintaining a network configuration that minimizes
unnecessary data traffic. When the bridge receives a packet, it creates a record containing the
MAC address (which differentiates the bridge from other network devices) and the physical
port it receives the frame on in a dynamic table. Wireless bridges, however, will forward all
broadcast frames.
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